Alan F. Hamlet Philip W. Mote Martyn Clark Dennis P. Lettenmaier
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Transcript of Alan F. Hamlet Philip W. Mote Martyn Clark Dennis P. Lettenmaier
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Alan F. HamletPhilip W. MoteMartyn Clark
Dennis P. Lettenmaier
JISAO/SMA Climate Impacts Groupand Department of Civil and Environmental Engineering
University of Washington
March, 2004
Effects of Temperature and Precipitation Variability on Snowpack
Trends in the Mountain West
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Current Climate 2020s 2040s
Snow Water Equivalent (mm)
VIC Simulations of April 1 Average Snow Water Equivalentfor Composite Scenarios (average of four GCM scenarios)
Climate Change in the WestThe main impact pathway : less snow
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Infl
ow
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re-f
t) Simulated 20thCentury Climate
2020s ClimateChange Scenario
2040s ClimateChange Scenario
Effects to the Cedar River (Seattle Water Supply)for “Middle-of-the-Road” Scenarios
+1.7 C
+2.5 C
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Linear Trends in Obs. April 1 SWE from 1950-1997From Snow Course Data
Source: Mote et al. (2004)
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Snowmelt runoff timing trends, 1948-2000
Graphic provided by Dan Cayan, Scripps Institute of Oceanography and the USGS. To appear in Climatic Change, 2003
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Ap
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Effects of the PDO and ENSO on Columbia River Summer Streamflows
Cool CoolWarm Warm
high highlow low
Ocean Productivity
PDO
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Snow Model
Schematic of VIC Hydrologic Model and Energy Balance Snow Model
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Preprocessing Regridding
Lapse Temperatures
Correction to RemoveTemporal
Inhomogeneities
HCN/HCCDMonthly Data
Topographic Correction forPrecipitation
Coop Daily Data
PRISM MonthlyPrecipitation
Maps
Schematic Diagram for Data Processing of VIC Meteorological Driving Data
Preprocessing Regridding
Lapse Temperatures
Correction to RemoveTemporal
Inhomogeneities
HCN/HCCDMonthly Data
Topographic Correction forPrecipitation
Coop Daily Data
PRISM MonthlyPrecipitation
Maps
Preprocessing Regridding
Lapse Temperatures
Correction to RemoveTemporal
Inhomogeneities
HCN/HCCDMonthly Data
Topographic Correction forPrecipitation
Coop Daily Data
PRISM MonthlyPrecipitation
Maps
Schematic Diagram for Data Processing of VIC Meteorological Driving Data
Result:Daily Precipitation, Tmax, Tmin
1915-1997
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Met Data1915-1997
VIC SWELinear Trend
Analysis
Overview of Simulation and Analysis
•1916-1997 •1924-1946 (cool to warm PDO)•1947-1997 (warm to cool PDO)•1924-1946 with 1977-1995 (warm to warm PDO)
Linear Trends:
Experiments:•Base—combined effects of temp and precip trends•Static Precip—effects of temperature trends only•Static Temp—effects of precipitation trends only
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Source: Mote et al. (2004)
Trends in April 1 SWE 1950-1997
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Trend %/yr
djf
avg
T (
C)
Trend %/yr
Trend Results
Red = PNWBlue = CAGreen = COBlack = GBAS
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Fig 31916-1997
A)
B)
C)
Trend %/yr
Trend %/yr
Trend %/yr
djf
avg
T (
C)
djf
avg
T (
C)
djf
avg
T (
C)
Trend %/yr
Trend %/yr
Trend %/yr
Both Temp and Precip
Precip Effects Only
Temp Effects Only
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Fig 41924-1976
A)
B)
C)
Trend %/yr
Trend %/yr
Trend %/yr
djf
avg
T (
C)
djf
avg
T (
C)
djf
avg
T (
C)
Trend %/yr
Trend %/yr
Trend %/yr
Both Temp and Precip
Precip Effects Only
Temp Effects Only
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Fig 51947-1997
A)
B)
C)
Trend %/yr
Trend %/yr
Trend %/yr
djf
avg
T (
C)
djf
avg
T (
C)
djf
avg
T (
C)
Trend %/yr
Trend %/yr
Trend %/yr
Both Temp and Precip
Precip Effects Only
Temp Effects Only
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Fig 61924-1946with1977-1995
A)
B)
C)
Trend %/yr
Trend %/yr
Trend %/yr
djf
avg
T (
C)
djf
avg
T (
C)
djf
avg
T (
C)
Trend %/yr
Trend %/yr
Trend %/yr
Both Temp and Precip
Precip Effects Only
Temp Effects Only
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Physical Characteristics of the Mountain West
Elevation (m) DJF Temp (C) NDJFM PCP (mm)
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Figure 7
1
2
3
Region 1 (Coastal)Region 2 (Inland)Region 3 (Interior)
Region 1
Region 2
Region 3
Trend %/yr
Trend %/yr
Trend %/yr
Trend %/yr
djfa
vgT
(C
)
Trends from 1916-1997
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Dworshak
y = 0.0001x + 0.7149
0.5
0.6
0.7
0.8
0.9
streamflow
Linear (streamflow)
Dworshak
y = -0.0006x + 0.506
0.3
0.4
0.5
0.6
0.7
0.8
streamflow
Linear (streamflow)
May-Sept
June-Sept
Fraction of Annual RunoffOccurring From:
BASE
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Dworshak
y = -0.0004x + 0.7493
0.5
0.6
0.7
0.8
0.9
streamflow
Linear (streamflow)
Dworshak
y = -0.0008x + 0.5072
0.3
0.4
0.5
0.6
0.7
0.8
streamflow
Linear (streamflow)
May-Sept
June-Sept
STATIC PRECIP
Fraction of Annual RunoffOccurring From:
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Conclusions
The Western US is experiencing losses of SWE in sensitive areas (such as coastal mountain ranges) due to observed regional warming.
Without precipitation trends, essentially the entire mountain west would be experiencing declines in April 1 SWE due to large-scale warming.
Precipitation trends are the major driver in areas with cold winter temperatures.
Precipitation trends seem to be most strongly associated with regionally-specific decadal scale climate variability. A consistent global warming signal for precipitation across the West is not apparent.
Decadal variability is apparently not a good explanation for losses of snowpack associated with temperature trends. (E.g. any period paired with 1977-1997 will show negative trends in SWE associated with temperature).
These results are consistent with the broad features of many global warming scenarios—i.e. rapid warming since the mid 1970s, modest increases in winter precipitation, streamflow timing shifts.